1. Field of the invention
This invention relates, in general, to air conditioning apparatus. In particular, the invention relates to a heat-pump type air conditioning apparatus including a central unit which supplies a conditioned air into a defined space through an air duct.
2. Description of the related art
A well known air conditioning apparatus of the above type typically includes a central unit which is partitioned into an internal air flow chamber and an external air flow chamber by a partition wall. An internal heat-exchanger and an internal fan device arranged parallel to the heat-exchanger are disposed in the internal air flow chamber to provide conditioned air into a defined space through the internal heat-exchanger. A compressor is arranged in a compartment defined in the internal air flow chamber to prevent heat and noises from the compressor from exhausting into the internal air flow chamber. An external heat-exchanger, an external fan device arranged parallel to the external heat-exchanger, etc. are disposed in the external air flow chamber. An exhausting damper and a ventilating damper are respectively arranged to the partition wall. Air in the internaI air flow chamber is discharged to the external air flow chamber through the exhausting damper when the exhausting damper is opened. Air in the external air flow chamber is taken into the internal air flow chamber through the ventilating damper when the ventilating damper is opened. Therefore, air in the defined space is exhausted through the internaI air flow chamber and the external air flow chamber when the exhausting and ventilating dampers are operated. A circulating air intake cell is disposed at the upper part of the internal air flow chamber, and an external air intake cell is disposed at the lower part of the external air flow chamber. A circulating damper is disposed between the circulating air intake cell and the internal air flow chamber for controlling the amount of air circulating into the internal air flow chamber. An external air intake damper is disposed between the external air intake cell and the external air flow chamber to control an amount of an external air into the external air flow chamber. The exhausting damper and the external air intake damper are closed in the cooling operation, the heating operation, and the defrosting operation.
In the above-described air conditioning apparatus, the amount of carbonic acid gas in the defined space is detected by a sensor during cooling or heating. The exhausting damper and the external air intake damper are opened when carbonic acid gas detected by the sensor is above a predetermined level. Therefore, a part of the circulating air flowing into the circulating air intake cell is discharged to the external air flow chamber through the exhausting damper. Simultaneously, a part of the external air flowing into the external air intake cell is taken into the internal air flow chamber through the external air intake damper. Thus, the ventilating operation is carried out, as described above.
In the above-described air conditioner, frost may be adhered on the external heat-exchanger of the central unit while the heating operation is carried out. In order to remove frost from the external heat-exchanger, the four-way valve is operated, and thus, a hot gas (refrigerant) fed from the compressor is supplied to the external heat-exchanger. Therefore, the external heat-exchanger acts as a condenser to evaporate the frost thereon. However, since the internal heat-exchanger acts as an evaporator during the defrosting operation, cold air is supplied into the defined space in spite of heating the defined space.
To avoid the above-described problem, two different refrigerating circuits are arranged in the central unit. If the defrosting operation is needed in one of two different refrigerating circuits during the heating operation, the one refrigerating circuit begins the defrosting operation, and the other refrigerating circuit continues the heating operation. Cold air fed from the one refrigerating circuit which carries out the defrosting operation, and hot air fed from the other refrigerating circuit are mixed tO control the temperature of the conditioned air flowing into the defined space from the central unit. The temperature of the conditioned air is regulated at substantially the same level as that in the defined space. Therefore, flow of the cold air into the defined space may be avoided.
However, in the above-described system, the above-described ventilating operation may be carried out in the other refrigerating circuit which continues the heating operation while the defrosting operation is carried out in the one of the refrigerating circuits. When the ventilating operation begins in the other refrigerating circuit, external air having a relatively low temperature flows into the internal air flow chamber, and is mixed with the circulating air, resulting in decrease in the temperature of the conditioned air flowing into the defined space. The temperature in the defined space also decreases.